From the Australian patent specification No. 567 839 it is known to use, in a thermal binding machine, a manual device for determining which cover dimension to be used for the the wad of papers to bound. The wad-receiving means of the known apparatus is formed as a plate mounted at the front edge of the binding machine and provided with a handle, the plate being displaceable towards the front edge. For determining the thickness of a wad of papers, said wad of papers is inserted between the handle and the front edge of the machine, then the plate will be manually displaced such that the wad of papers is pressed by the handle towards said front edge. The plast is mechanically connected to a potentiometer such as to provide position detection. The position-indicating voltage value given by the potentiometer is used to light, accordingly, a series of light emitting diodes, LEDs, or liquid crystal diodes, LCDs, forming a display. Thereby, the display can indicate the thickness either in mm or in inches, and is said to indicate, to advantage, the directly required cover dimension.
The known manual device presents a number of disadvantages. Firstly, it should be pointed out that said device is unreliable, as manual displacement of the plate implies that the wad of papers can be compressed unequally hard, meaning that you may receive different answers as to what cover dimension is required. The operator having to use both hands to handle the manual device is another troublesome disadvantage. Further, manual handling is relatively time-consuming and implies exterior movable parts which are easily damaged and, not least, require more space for the machine.